Footage shows a group of men armed with bats fighting outside a Smyths Toys Superstore in southeast London.
The group were fighting next to a large queue of people reportedly waiting to pick up the newly-released Pokémon 'Prismatic Evolution' trading card pack, with purchases being limited to one per person.
According to reports online, fighting broke out over attempts to queue jump, although this has not been confirmed.
Footage circulating online shows a man chasing and striking others with a weapon before one man falls to the ground.
Police were called to the incident just before 9am on Friday.
A 43-year-old man was arrested on suspicion of possession of an offensive weapon, police say.
A spokesperson for Met Police said: “Police were called at 08.54hrs on Friday, 12 June to a group of men fighting with bats on Old Kent Road, Southwark.
“Officers were at the scene within three minutes, where a 43-year-old man was arrested on suspicion of possession of an offensive weapon.
“He remains in custody. No injuries have been reported.
“Enquiries continue.
“Anyone with information that could help police should call 101 quoting CAD 1752/12Jun.”